Interference fit fasteners are used in many critical situations and must be properly installed. This is particularly important in the construction of aircraft where structural integrity and safety are of primary importance. Excessive stress on a fastener can weaken the fastener or damage the structure of the component being built. Conversely failure to fully seat a fastener can lead to a weakened area in the structure and may even come loose causing serious safety problems.
Fasteners used in interference fit situations are generally installed with pull guns that draw the fastener into a hole until it is seated. The pull gun has a mandrel that is first threaded into the end of the fastener. The mandrel is then hydraulically pulled back until the fastener seats in the hole.
While these pull guns are efficient and fast they present problems if not properly operated. If an operator does not stop soon enough excessive hydraulic force can be applied damaging the structure or the fastener. If stopped too soon, it may be pulled too little leaving a loose fastener. If a loose fastener is detected, it may be corrected. However, a fastener that is pulled too much may lead to more serious problems. If fastener or structure damage is evident then the part may have to be scrapped causing a substantial loss. Perhaps a more serious problem of safety presents itself if the damage is not detected. For example, a potentially defective aircraft part may be produced. It is therefore very important that interference fit fasteners be set properly.
These problems result from the installation of these fasteners being dependent upon the skill of the pull gun operator. They must have the skill to know when the fastener has been set properly. Having to know this can also reduce efficiency as the operator must take care. It would be advantageous if a properly set fastener could be produced automatically and efficiently. It would reduce assembly time and as a result costs but would also improve quality.
It is therefore one object of the present invention to provide a computer controlled interference fit fastener pull gun system that will correctly install a fastener automatically.
Still another object of the invention is to provide a computer controlled interference fit pull gun system that will abort when a fastener is not properly installed.
Accordingly, another object of the invention is to provide a fastener pull gun system that will stop when the fastener is properly installed.
Another object of the invention is to provide a fastener pull gun system that is less dependent on operator skill.
Another object of the invention is to provide a fastener pull gun that will automatically complete and stop an operation at the proper time when started.
Another object is to provide a fastener pull gun that will quickly and efficiently pull a fastener into an interference fit hole and stop when the fastener is properly seated.